Vibrator

ABSTRACT

A vibrator, particularly for the manufacture of moulded concrete products, comprises a support for a mass to be vibrated and means for vibrating the support; said means including a reciprocable member having an elastic portion for increasing the acceleration of the support during vibration thereof when it is near its extreme positions of vibration.

United States Patent Sironi [4 1 Dec.5, 1972 [30] Foreign ApplicationPriority Data 3,151,958 10/1964 Bodine ..2s9/ 1 R 1,279,368 9/1913Landon ..2s9/1 R 3,532,325 10/1970 Barnett ..259/1 R PrimaryExaminer-Robert W. Jenkins Attorney-Woodhams, Blanchard and Flynn [57]ABSTRACT A vibrator, particularly for the manufacture of mouldedconcrete products, comprises a support for a mass to be vibrated andmeans for vibrating the support, said means including a reciprocablemember having an elastic portion for increasing the acceleration of thesupport during vibration thereof when it is near its extreme positionsof vibration;

10 Claims, 4 Drawing Figures Nov. 21, 1969 France ..6940115 [52] US. Cl...259/1 R, 259/DIG. 43, 259/72 [5 1] Int. Cl. ..B01f 9/00 [58] Field ofSearch ..259/l R, 72, DIG. 43, DIG. 44, 259/9l, 92

[56] References Cited UNITED STATES PATENTS 1,017,685 2/1912 Mumford..259/l R 1p I I PATENTED EB we 3.704.862

SHEET 1 UP 2 PATENTEU DEC 5197? 3. 704.88 2

' sum 2 IF 2 1 VIBRATOR This invention relates to a vibrator, forexample for the manufacture of moulded concrete products.

In a known vibrator for vibrating moulded concrete products, a supporttable is vibrated sinusoidally with time. This has the consequence thatthe acceleration of said support is likewise a sinusoidal function oftime. This gives rise to the disadvantage that, since the frequency ofoperation of the installation is low, acceleration is always rather poorand is even equal to zero during the changing of the direction ofmovement of the piston. This makes it impossible to obtain highefficiency in operation, particularly in a concrete vibrationinstallation in which the movable support is moved vertically and inwhich it is necessary for the acceleration to have a value very close tothat of gravity in order to enable the mass to be vibrated to behavelike a fluid and for its components to be distributed homogeneously.

In orderto increase the acceleration of the movable support table, itmay be thought that it is sufficient to increase the frequency of thevibrations, since acceleration is proportional to the square of thefrequency. This however is not possible in practice, because thisfrequency must be selected above all in dependence on the composition ofthe material of the mass to be vibrated. This would in addition entailthe serious disadvantage of making it necessary to work in the range ofaudible frequencies, which is impossible to contemplate because of theconsiderable energy involved. Furthermore, in order to enable theacceleration near the point of reversal of the direction of sup portmovement to approach the acceleration due to gravity, it would benecessary to select a frequency such that acceleration at mid-strokewould be much higher than that due to gravity. Experience has shown thatthis would result in a segregation of the constituents in the mass ofmaterial, which is the contrary ofthe result desired.

The present invention may provide a vibrator which is less subject tothe above disadvantages.

According to the present invention, a vibrator comprises a support for amass to be vibrated and means for vibrating the support; said meansincluding a reciprocable member having an elastic portion for increasingthe acceleration of the support during vibration thereof when it is nearits extreme positions of vibration.

By increasing the acceleration we mean relative to the acceleration thesupport would have when near its extreme positions of vibration, if theelastic portion were not provided.

In a preferred embodiment, the reciprocable member is a connecting rod,the elasticportion being a portion of the rod, the length of which canvary in dependence upon compressive and tractive forces to which it issubjected in operation.

The connecting rod may be arranged to drive a piston, the pistoncommunicating with a chamber adapted to contain a liquid, said chamberbeing bounded by a movable member connected to the support so'that inoperation vibrations of the piston are transmitted through the liquid tothe support.

The movable member may be a flexible diaphragm.

The elastic portion may comprise two relatively movable parts, oneattached to one end of theconnecting rod the other attached to the otherend of the connecting rod, and at least one elastic element acting uponthe two parts to bias them towards a predetermined relative positionwhich is intermediate extreme relative positions between which the partsmay relatively move.

The one relatively movable part may be a hollow cylinder, the otherrelative movable part being a piston disposed therein, the elasticelement being a spring within the cylinder.

The support may be a table.

The invention will be described, merely by way of example, withreference to the accompanying drawings, wherein FIG. 1 illustratesdiagrammatically a concrete vibrator installation according to theinvention;

FIG. 2 is an axial section of part of the installation of FIG. 1;

FIG. 3 is a diagram showing the variation of the position of the pistonplotted against time in a prior art vibrator; and

FIG. 4 shows a corresponding diagram obtained in a vibrator according tothe invention.

The installation illustrated in FIG. 1 comprises a vertical cylindricalcontainer 1 disposed on a rigid foundation 2 and containing an internalcoaxial cylinder 3 the bottom of which is constituted by the bottom 4 ofthe container. An annular chamber capable of being filled with a liquid5, for example oil, is thus available around the cylinder 3. Thischamber is closed at the top by a movable closure wall constituted by aflexible diaphragm 6. The periphery of this diaphragm is fastenedsealingly in a circular groove 7 formed in the edge of the container 1,and its central portion is fastened, likewise sealingly, in a circulargroove formed in a thickened portion 8 of the cylinder 3. The annularportion of said diaphragm 6 is consequently movable in a verticaldirection under the action of the pressure of the liquid 5.

A guide piston 9 fastened at the top to a ring 10 by a clamp nut 11 isadapted to slide in the cylinder 3. said ring 10 being solid with amovable support table 12 intended to support a mass of concrete to bevibrated. The bottom surface of the ring 10' rests on the annularportion of the flexible diaphragm 6, so that the movements of saiddiaphragm are transmitted to the movable support 12, which is thusultimately carried by the liquid 5. The container 1 is in communicationwith a lateral cylinder 13 the axis of which is horizontal and in whicha piston 14 is adapted to move. Said piston is driven by a connectingrod represented generally by 15, its big end 16 being connected to arotary driving element constituted by a pulley 1'7. Said pulley isdriven rotationally by a motor 18 and a belt 19. The big end of theconnecting rod is adapted to slide radially in a slot 20 in the pulley,thus enabling it to be fixed at different distances from the center, soas to adjust the stroke of the piston 14 in known manner.

The arm of the connecting rod 15 is composed of two rigid portions 21and 22 connected by an elastic portion 23, which is illustrated ingreater detail in FIG. 2. This elastic portion comprises a piston 24connected to the connecting rod big end by the rigid portion 22, saidpiston being adapted to slide in a cylinder 25. This cylinder is closedat both ends by screw stoppers 26a and 26b. The stopper 26a is fixed tothe rigid portion 21, thus enabling the cylinder 25 to be joined to theportion 21 connected to the connecting rod little end.

Each of the faces of the piston 24 is provided with a groove 27receiving the end of a coil spring 28a and 28b bearing respectivelyagainst the stoppers 26a and 26b. The piston 24 and cylinder 25 can moverelative to each other in both axial directions against the action ofthe springs 28a, 28b. The springs apply opposite forces to the slidingpart 24 and when the elastic portion is not subjected to anylongitudinal stress these opposite forces tend to hold the piston 24 andcylinder 25 in an intermediate relative position as shown in FIG. 2. Theforce applied by the springs 28a and 28b can be adjusted by screwing inor out the stoppers 26a and 26b, which thus serve as adjustment means inaddition to their function as abutments.

The operation of the vibrator is as follows. The driving element 17 .isdriven in the direction shown by the arrow in a uniform rotary movementby the motor 18 and the belt 19. It follows that the component of thedisplacement of the big end 16 of the connecting rod in a horizontalplane varies in accordance with a sinusoidal function of time. This hasthe consequence that if the arm of the connecting rod 15 were entirelyrigid thedisplacement of the piston 14 in the cylinder 13 would alsovary in accordance with a sinusoidal function of time, as illustrated inFIG. 3, which would entail the disadvantages described above.

The effect of the elastic portion 23 disposed between the rigid portions21 and 22 will now be discussed. The movement during which theconnecting rod 15 moves in the direction of the cylinder 13 will becalled the forward movement and the movement during which the connectingrod 15 moves in the opposite direction will be called the returnmovement.

In the forward movement, during which the connecting rod 15 is subjectedto a compressive stress, the length of the elastic portion 23 isdecreased and, since its spring 28a is compressed elastically, energy isstored. When the connecting rod arrives at the end of the forward stroke(with the big end 16 at B) the component of its movement in thedirection of the displacement of the piston 14 is zero. The compressivestress to which the connecting rod is subjected thus is interrupted andthe spring 28a expands abruptly, releasing its stored energy. The piston14 therefore continues forwards solely through the impetus provided bythe expansion of the elastic portion 23. Meanwhile, the connecting rodportion 21 has started its return movement, and the piston 14consequently stops and reverses abruptly when the elastic portion 23 hasexpanded to its unstressed length.

In the return movement, during which the connecting rod is subjected toa tractive stress, the length of the elastic portion 23 increases andthe spring 28b is compressed, storing energy. When the connecting rodbig end 16 arrives at A at the end of the return stroke and thecomponent of movement of the connecting rod 15 in the direction of thedisplacement of the piston 14 is again zero, the tractive stress towhich the connecting rod is subjected is interrupted and the elasticportion 23 abruptly regains its normal length, the spring 28b expandingand releasing the energy which it had stored. The piston 14 thereforecontinues its stroke in the rearward direction, stopping and reversingabruptly when the elastic portion has regained its normal length. Thecycle then starts again.

It is thus seen that the elastic portion 23 of variable length storesenergy in the middle of the forward and return strokes and gives up thisenergy at the end of the strokes. This has the consequence that for agiven speed of rotation of the driving element the acceleration of thepiston 14 is reduced towards the middle of each of its strokes andincreased at the end of the stroke. It can be seen that in this way theshortcomings entailed by a sinusoidal movement can be compensated, theseshortcomings being that the acceleration is maximum at mid-stroke andzero at the end of the stroke. In the illustrated vibrator theacceleration of the piston (and therefore of the movable support 12) ispractically constant, the direction of this acceleration being abruptlyreversed at the ends of the stroke.

The movement of the piston 14 in the cylinder 13 complies with thefunction illustrated in FIG. 4, which is a corrected sinusoid, themaxima being sharper and the change of direction at A and B beingeffected practically without passing through a zero slope. The movablesupport table 12 is displaced vertically' in accordance with the samefunction, the liquid 5 being substantially incompressible. Thus, theelastic portion 23 increases the acceleration of the support table 12near its extreme positions of vibration, compared to the accelerationthat the support table would have if the elastic portion 23 were notprovided.

It is obvious that the frequency of the cyclic vibrations to which thesupport table is subjected can easily be regulated by modifying thespeed of the motor 18. It is thus possible for the frequency of thereciprocating movement of the piston to be judiciously selected from therange of low inaudible frequencies, in such a manner that theacceleration of the table 12 will always be close to the optimum value,while remaining compatible with the composition of the material to bevibrated.

Also, the amplitude of the vibrations can be adjusted by modifying theradial position of the connecting rod big end 16, thereby determiningthe stroke of the piston 14 and consequently the amount of fluid movinginto and out of the chamber in each cycle, thereby determining thevertical stroke of the support table.

It has in particular been found that the installation described abovepermits effective vibration of concrete of normal composition with afrequency of 15 ds and an amplitude of support displacement of 2millimeters lclaim:

l. A vibrator comprising:

a support for a mass to be vibrated;

means for vibrating said support;

said means for vibrating said support including reciprocal member meansoperatively interconnected to said support for vibrating same inresponse to reciprocation of said member means; and

said reciprocal member means including elastically deformable means forincreasing the acceleration of the support during the vibration thereofwhen said reciprocal member means is near its extreme position ofmotion.

2. A vibrator according to claim 1, wherein said reciprocal member meanscomprises rod means having a length which is variable during operationof the vibrator, said elastically deformable means being a portion ofsaid rod means with the length of said elastically deformable meansvarying in dependence on the compressive and tractive forces appliedthereto during operation of the vibrator.

3. A vibrator according to claim 2, wherein said rod means includesfirst and second rod portions and said elastically deformable means isconnected between the adjacent ends of said first and second rodportions for permitting relative movement therebetween during operationof the vibrator, said elastically deformable means including a firstpart attached to the end of said first rod portion and a second partattached to the end of said second rod portion, said elasticallydeformable means also including resilient biasing means coacting betweensaid first and second parts for biasing said first andsecond partstoward a predetermined relative position which is intermediate theextreme relative positions between which the first and second parts mayrelatively move.

4. A vibrator as claimed in claim 3 wherein one relatively-movable partis a hollow cylinder, the other relatively moveable part being a pistondisposed therein, the resilient biasing means being a spring within thecylinder.

5. A vibrator as claimed in claim 2 comprising a chamber adapted tocontain a liquid, a piston bounding the chamber, the rod means beingarranged to drive the piston, a movable member also bounding the chamberand being connected to the support whereby vibrations of the piston aretransmitted through the liquid to the support.

6. A vibrator as claimed in claim 5 wherein the movable member is aflexible diaphragm.

7. A vibrator according to claim 2, further including a rotatable drivecrank, and said rod means comprising an elongated multipart connectingrod having one end thereof pivotally connected to said crank, the otherend of said connecting rod being constrained for linear reciprocatingmovement.

8. A vibrator as claimed in claim 1 wherein the sup port is a table.

9. A vibrator, comprising a support for a mass to be vibrated,- andmeans for vibrating the support, said means for vibrating the supportincluding reciprocal member means operatively interconnected to saidsupport for vibrating same in response to reciprocation of said membermeans, said reciprocal member means including means responsive to thecompressive and tractive forces imposed on said member means duringoperation of said vibrator for causing the length of said reciprocalmember means to vary during the cyclic operation thereof.

10. A vibrator according to claim 9, wherein said reciprocal membermeans includes first and second portions operatively interconnected forpermitting a predetermined amount of relative linear movementtherebetween for permitting the length of said member means to varyduring the cyclic movement of said member means.

1. A vibrator comprising: a support for a mass to be vibrated; means forvibrating said support; said means for vibrating said support includingreciprocal member means operatively interconnected to said support forvibrating same in response to reciprocation of said member means; andsaid reciprocal member means including elastically deformable means forincreasing the acceleration of the support during the vibration thereofwhen said reciprocal member means is near its extreme position ofmotion.
 2. A vibrator according to claim 1, wherein said reciprocalmember means comprises rod means having a length which is variableduring operation of the vibrator, said elastically deformable meansbeing a portion of said rod means with the length of said elasticallydeformable means varying in dependence on the compressive and tractiveforces applied thereto during operation of the vibrator.
 3. A vibratoraccording to claim 2, wherein said rod means includes first and secondrod portions and said elastically deformable means is connected betweenthe adjacent ends of said first and second rod portions for permittingrelative movement therebetween during operation of the vibrator, saidelastically deformable means including a first part attached to the endof said first rod portion and a second part attached to the end of saidsecond rod portion, said elastically deformable means also includingresilient biasing means coacting between said first and second parts forbiasing said first and second parts toward a predetermined relativeposition which is intermediate the extreme relative positions betweenwhich the first and second parts may relatively move.
 4. A vibrator asclaimed in claim 3 wherein one relatively movable part is a hollowcylinder, the other relatively moveable part being a piston disposedtherein, the resilient biasing means being a spring within the cylinder.5. A vibrator as claimed in claim 2 comprising a chamber adapted tocontain a liquid, a piston bounding the chamber, the rod means beingarranged to drive the piston, a movable member also bounding the chamberand being connected to the support whereby vibrations of the piston aretransmitted through the liquid to the support.
 6. A vibrator as claimedin claim 5 wherein the movable member is a flexible diaphragm.
 7. AvibrAtor according to claim 2, further including a rotatable drivecrank, and said rod means comprising an elongated multipart connectingrod having one end thereof pivotally connected to said crank, the otherend of said connecting rod being constrained for linear reciprocatingmovement.
 8. A vibrator as claimed in claim 1 wherein the support is atable.
 9. A vibrator, comprising a support for a mass to be vibrated,and means for vibrating the support, said means for vibrating thesupport including reciprocal member means operatively interconnected tosaid support for vibrating same in response to reciprocation of saidmember means, said reciprocal member means including means responsive tothe compressive and tractive forces imposed on said member means duringoperation of said vibrator for causing the length of said reciprocalmember means to vary during the cyclic operation thereof.
 10. A vibratoraccording to claim 9, wherein said reciprocal member means includesfirst and second portions operatively interconnected for permitting apredetermined amount of relative linear movement therebetween forpermitting the length of said member means to vary during the cyclicmovement of said member means.